Half sandwich titanocenes, e.g . (ind)TiRCl 2 (R—Cl, OMe, OEt; ind—indenyl group) and β diketonate titanium complexes, e.g . (dbm) 3TiL (L—Cl, OPh, OPhMe; dbm—dibenzoylmethane group) were investigated for syndiotactic polymerization of styrene. The optimum molar ratios of Al to Ti of β diketonate titanium complexes were different from those of mono indenyl titanium complexes. The polymerization activity of (ind)TiRCl 2 was higher than that of (dbm) 3TiL at their own optimum n (Al)/ n (Ti). Compared with (ind)TiRCl 2, the thermostability of (dbm) 3TiL was higher. The polymerization activity of (dbm) 3Ti(OPh) was 6 5×10 5 g/(mol·h) at 363 K, while that of (ind)Ti(OMe)Cl 2 was only 4 9×10 5 g/(mol·h) at the same temperature. After 2 h of polymerization, the reaction activity of the nontitanocene was remained at 6×10 5 g/(mol·h), while that of the half sandwich titanocene was only 0 71×10 5 g/(mol·h). It is indicated that the life time of (dbm) 3TiL was much longer than that of (ind)TiRCl 2. The melting temperatures ( T m) and the syndiotacticity of polystyrene by β diketonate titanium complexes were higher than those of the polymer by mono indenyl titanium complexes as well.
